Method of forging titanium alloy billets



United States Patent This invention relates to a method of forging billets of alpha-beta titanium-base alloys. It has hitherto been the commercial practice to forge billets of such alloys by using flat forging dies and heating the billets to above the beta transus temperature of the alloy before forging. When such alloys are to be used to make complex close die forgings which, because of their size, receive little work or are subject to surface cracking during some part of the forging operation, it has been observed that the billet tends to develop a coarse grain size in its surface layers, with the result that extensive, time-consuming conditioning is required before the forging can be used or further forged. Moreover, at times the tensile ductility of the forging is less than optimal. We have discovered that these difiiculties can in large measure be overcome or avoided by using a V-die, rather than a flat die, and conducting the forging operation at a temperature below the beta transus temperature of the alpha-beta alloy being worked. We have also discovered that, for optimal reduction in cross-sectional area of the billet in drawing it to final size after the forging operation, it is preferable, although not absolutely essential, that the billets to be forged be upset.

A complete understanding of our invention may be had from the following detailed description thereof, illustrating with specific examples the best mode presently contemplated by us for its practice.

Example 1.-An ingot of alpha-beta titanium alloy (6% aluminum, 4% vanadium, ba-lance titanium) 32 inches in diameter and about 80 inches long was heated to about 2050 F. It was then placed on end in a forging press and upset to reduce its height by about 35% of its original length. The upset ingot was reheated to about 2050 F., and then drawn, in accordance with conventional practices, to a square of about 26 inches by 26 inches. This piece was then conditioned by swing grinding, heated to 1750 F., and drawn down to a 24-inch octagon. The octagon was reheated to about 1750 F., and then press-forged to a 22-inch diameter round, using a V-die. The sides of the V-die were at about a 45 angle with the horizontal. During the V-die forging, the workpiece was reheated to 1750 F. only as necessary, soaking being avoided. The workpiece was then skinground, grit-blasted, tested, and prepared for shipment.

Example 2.-Example 1 was repeated, except that after being conditioned by using a swing grinder and being heated to 1750" F., the workpiece was drawn down to a 20-inch octagon, reheated to 1750 F., and then pressforged, using a V-die, to a final size of 18 inches diameter.

The product of both the above examples exhibited a finer grain size than. do pieces of similar size produced by the usual practice of fiat-die forging at temperatures above the beta transus. The advantage of producing forgings of fine grain size is Well known in the art. Fine grain size imparts superior toughness and ductility to the forgings. To achieve this result with the method of the present invention, it is critical that the workpiece be forged at a temperature below the beta transus temperature of the alloy of the workpiece by simultaneously applying forces directly radially inward toward the longitudinal axis of the workpiece by means of at least three separate and distinct contacting surfaces arranged longitudinally 3,313,138. Patented Apr. 11, 1967 along the workpiece and'spaced substantially evenly about the periphery thereof. More specifically, this is achieved by the use of a V-shaped die.

Our invention finds use with all alpha-beta titaniumbase alloys, including the 6Al-4V alloy mentioned above as well as the 4Al-4Mn and the 7Al-4Mo alloys. Certain alloys that are considered alpha alloys but contain a small amount of beta micro-structure, such as Ti-8Al-lMo-1V, may also be processed in accordance with our invention.

The exact temperature to be used in each of the heating steps indicated above will depend upon the composition, and more specifically upon the beta transus temperature, of the specific alloy being worked. Variations in and modifications of the practices disclosed in the above examples will be discussed with reference to the 6Al-4V alloy, which has a beta transus temperature of about 1850 F.

It is desirable that the upsetting operation be conducted at about 2000 to 2100". With lower temperatures, the workpiece tends to be hard to upset, and with higher temperatures, hydrogen contamination of the surface of the workpiece is likely to be encountered.

For optimal performance in reduction of the crosssectional area of the workpiece to final size, it is desirable to upset the ingot about 35% of its original length, although substantial benefits can be obtained with upsets as low as 20% and as high as 50%.

It is important that the V-die forging step be done at a temperature below the beta transus temperature, preferably about to F. below the beta transus temperature. It is also essential that a V-die having sides that make a substantial acute angle with the horizontal, such as about 30 to 60%, be used. Either a press forge or a hammer forge can be used.

Although the invention has been described above with reference to the use of a V-shaped forging die, it will be apparent to those skilled in the art that other means can be used whereby substantially the same action and result are obtained, e.g., positioning three or more contacting members, contacting faces or surfaces substantially evenly about the periphery of the workpiece and simultaneously applying by means of them radially inwardly directed forces to form, forge, or otherwise substantially work the workpiece at a temperature below the beta transus.

It is essential that a certain amount of work be done on the workpiece in the V-die forging step; i.e., it is essential that such step reduce the, cross-sectional area of the workpiece by at least 10% or more, up to 50%, preferably about 30%. Also, it is possible to conduct some,

or even most, of the V-die forging step at temperatures above the beta transus, so long as such forging is followed by forging below the beta transus temperature to the extent of at least 10% reduction in cross-sectional area as a final part of the V-die forging step.

Although our invention has been described with respect to certain specific practices, it will be readily apparent to those skilled in the art that various modifications therein may be made to suit specific requirements without departing from the spirit and scope of the invention.

We claim: I

1. In a method of forging an alpha-beta titanium-base alloy billet, the step which comp-rises forging an elongated workpiece of said alloy at a temperature below the beta transus temperature of said alloy to such an extent as to reduce the cross-sectional area of said workpiece by about 10 to 50% by simultaneously applying forces directed radially inward toward the longitudinal axis of said workpiece by means of at least three separate and distinct contacting surfaces arranged longitudinally along said workpiece and spaced substantially evenly about the periphery of said workpiece.

2. A method of producing a forged billet of an alphabeta titanium-base alloy comprising in combination the steps of upsetting an elongated ingot of said alloy at a. temperature above the beta transus temperature of said alloy by about 20 to 50% of its original length, and then forging said alloy, at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce the cross-sectional area of said workpiece by about to 50%, by simultaneously apply forces directed radially inward toward the longitudinal axis of said ingot by means of at least three separate and distinct contacting surface arranged longitudnially along said ingot and spaced substantially evenly about the periphery of said ingot.

3. In a method of forging a billet of a titanium-base alloy selected from the group consisting of Ti-6Al-4V, Ti-4Al-4Mn, Ti-7Al-4Mo and Ti-8Al-1Mo-1V, the step which comprises forging an elongated workpiece of said alloy at a temperature below the beta transus temperature of said alloy to such an extent as to reduce the crosssectional area of said workpiece by about 10 to 50% by simultaneously applying forces directed radially inward toward the longitudinal axis of said workpiece by means of at least three separate and distinct contacting surfaces arranged longitudinally along said workpiece and spaced substantially evenly about the periphery of said workpiece.

4. A method of producing a forged billet of an alphabeta titanium-base alloy selected from the group consisting -of Ti-6A1-4V, Ti-4Al-4Mn, Ti-7Al-4Mo, Ti-8Al-1Mo-1V, comprising, in combination, the steps of upsetting an elongated ingot of said alloy at a temperature above the beta transus temperature of said alloy by about 20 to 50% of its original length, and then forging said alloy, at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce the cross-sectional area of said ingot by about 10 to 50%, by simultaneously applying forces directed radially inward toward the longitudinal axis of said ingot by means of at least three separate and distinct contacting surfaces arranged longitudinally along said ingot and spaced substantially evenly about the periphery of said ingot.

5. In a method of forging an alpha-beta titanium-base alloy billet, the step which compirses forging an elongated workpiece of said alloy at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce the cross-sectional area of said workpiece by about 10 to 50%, using a die V-shaped in longitudinal cross-section, the sides of' said die forming an angle of about 30 to 60 with the horizontal.

6. A method of producing a forged billet of a nalphabeta titanium-base alloy comprising, in combination, the steps of upsetting an elongated ingot of said alloy at a temperature-above the beta transus temperature of said alloy by about 20 to 50% of its original length, and then forging said alloy, at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce the cross-sectional area of said ingot by about 10 to 50%, using a die V-shaped in longitudinal crosssection, the sides of said die forming an'angle of about 30 to 60 with the horizontal.

' 7. In a method of forging a billet'of a titanium-base alloy selected from the group consisting of Ti-6Al-4V, Ti-4Al-4Mn, Ti-7Al-4Mo, and Ti-8Al-1Mo-1V, the step and beta titanium-base alloy selected from the group consisting of Ti-6Al-4V, Ti-4Al-4Mn, Ti-7Al-4Mo, and Ti-8A-lMo-1V, comprising, in combination, the steps of upsetting an elongated ingot of said alloy at a temperature above the beta transus temperature of said alloy by about 20 to 50% of its original length, and then forging said alloy, at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce' the cross-sectional area of said ingot by about 10 to 50%, using a die V-shaped in longitudinal crosssection, the sides of said die forming an angle of about 30 to 60 with the horizontal.

9. In a method of forging .a billet of a titanium base alloy consisting essentially of about 6% aluminum, 4% vanadium, balance titanium, the step which comprsies forging an elongated workpiece of said alloy at a temperature below the beta transus temperature of said alloy, to such. an extent as to reduce the cross-sectional area of said workpiece by about 10 to 50%, using a die V-shaped in longitudinal cross-section, the sides of said die forming an angle of about 30 to 60 with the horizontal.

10. A method of producing a forged billet of a titanium-base alloy consisting essentially of about 6% aluminum, 4% vanadium, balance titanium, said method comprising, in combination, the steps of upsetting an elongated ingot of said alloy at a temperature above the beta transus temperature of said alloy by about 20 to 50% of its original length, and then forging said alloy, at a temperature below the beta transus temperature of said alloy, to such an extent as to reduce the cross-sectional area of said ingot by about 10 to 50%, using a die V-shaped in longitudinal cross-section, the sides of said die forming an angle of about 30 to 60 with the horizontal.

11. A method of producing a forged billet of a titanium-base alloyconsisting essentially of about 6% aluminum, 4% vanadium, balance titanium, said method comprising, in combination, the steps of upsetting an elongated ingot of said alloy at about 2000 to 2100" F. by about 35% of its original length, and then forging said alloy at a temperature of about 1750 F., to such an extent as to reduce the cross-sectional area of said ingot by about 10 to 50%, using a die V-shaped in longitudinal cross-section, the sides of said die forming an angle of about 45 with the horizontal.

References Cited by the Examiner UNITED STATES PATENTS 144,832 11/1873 Coes 72-474 503,481 8/1893 Horn 72-374 2,950,191 8/1960 Vordahl 1481l.5 3,194,693 7/1965 Solitis 14811.5

CHARLES W. LANHAM, Primary Examiner. L. A. LARSON, Assistant Examiner. 

1. IN A METHOD OF FORGING AN ALPH-BETA TITANIUM-BASE ALLOY BILLET, THE STEP WHICH COMPRISES FORGING AN ELONGATED WORKPEICE OF SAID ALLOY AT A TEMPERATURE BELOW THE BETA TRANSUS TEMPERATURE OF SAID ALLOY TO SUCH AN EXTENT AS TO REDUCE THE CROSS-SECTIONAL AREA OF SAID WORKPIECE BY ABOUT 10 TO 50% BY SIMULATANEOUSLY APPLYING FORCES DIRECTED RADIALLY INWARD TOWARD THE LONGITUDINAL AXIS OF SAID WORKPIECE BY MEANS OF AT LEAST THREE SEPARATE AND DISTINCT CONTACTING SURFACES ARRANGED LONGITUDINALLY ALONG SAID WORKPIECE AND SPACED SUBSTANTIALLY EVENLY ABOUT THE PERIPHERY OF SAID WORKPIECE. 